1. Field of the Invention
The present invention relates to key switches with indicator lamp means for indicating an operated key.
2. Description of the Prior Art
Such a key device with indicator lamp means is used, for example, for selection key switches, such as office-line selection keys, extension line selection keys, hold keys or the like in a key telephone set.
A known key switch with indicator lamp means includes an insulator housing plate having an opening and an electric circuit board stationarily disposed inside the housing plate. A key is slidably fitted in the opening and is elastically supported therein. The key can be pushed down to the circuit board against the elastic support. The key is accompanied with a movable contact which moves together with the key. The circuit board has a pair of fixed contacts formed on its upper surface. The pair of fixed contacts is closed or connected with one another by the movable contact when the key is pushed down so that the movable contact comes into contact with the fixed contacts. In the vicinity of the pair of fixed contacts, a light emission diode device is mounted on the circuit board.
The circuit board is connected with an external control circuit (not shown) so that when the key is pushed down, the light emission diode device is energized or luminesces for indicating the operated key.
In the known key switch, the light emission diode device is used as an indicator lamp means, and is disposed in a space between the housing plate and the circuit board. Therefore, the space is determined by the size of the light emission diode device so that it is impossible to reduce a thickness or height of the key switch device.
Further, the circuit board must have through holes for receiving the leads of the light emission diode device and metal patterns on the bottom surface for soldering the leads thereto. Therefore, the circuit board is required to have metal patterns on both surfaces.